Medical science has advanced to the point where it is possible to implant directly within living bodies electrical devices necessary or advantageous to the welfare of individual patients. A problem with such devices is how to supply the electrical energy necessary for their continued operation. The devices are, of course, designed to require a minimum of electrical energy, so that extended operation from batteries may be possible. Lithium batteries and other primary, non-rechargeable cells may be used, but they are expensive and require replacement of surgical procedures. Nickel-cadmium and other rechargeable batteries are also available, but have limited charge-recharge characteristics, require long intervals for recharging, and release gas during the charging process.